Receptor innervation by ganglion cells. (Top) drawing that illustrates the segregated innervation of hair cells by the two types of spiral ganglion cells. Type II neurons represent only 5–10% of the population and innervate multiple outer hair cells. In contrast, type I neurons represent the remaining 90–95% and innervate exclusively inner hair cells. Each IHC is innervated by 10–20 ganglion cells. (Bottom) photomicrograph of representative type I and type II ganglion cells as stained by horseradish peroxidase [100] (Kiang, NY-S, Morest, DK, Godfrey, DA, et al. Stimulus coding at caudal levels of the cat's auditory nervous system. I. Response characteristics of single units. In: Basic Mechanisms of Hearing. AR Moller, eds. New York: Academic Press; 1973. pp. 455–478.)